SACRAMENTO, Calif. (AP) — Across the West, early miners digging for gold, silver and copper had no idea that one day something else very valuable would be buried in the piles of dirt and rocks they tossed aside.

There's a rush in the U.S. to find key components of cellphones, televisions, weapons systems, wind turbines, MRI machines and the regenerative brakes in hybrid cars, and old mine tailings piles just might be the answer. They may contain a group of versatile minerals the periodic table called rare earth elements.

"Uncle Sam could be sitting on a gold mine," said Larry Meinert, director of the mineral resource program for the U.S. Geological Survey in Reston, Va.

The USGS and Department of Energy are on a nationwide scramble for deposits of the elements that make magnets lighter, bring balanced hues to fluorescent lighting and color to the touch screens of smartphones in order to break the Chinese stranglehold on those supplies.

They were surprised to find that the critical elements could be in plain sight in piles of rubble otherwise considered eyesores and toxic waste. One era's junk could turn out to be this era's treasure.

"Those were almost never analyzed for anything other than what they were mining for," Meinert said. "If they turn out to be valuable that is a win-win on several fronts — getting us off our dependence on China and having a resource we didn't know about."

The 15 rare earth elements were discovered long after the gold rush began to wane, but demand for them only took off over the past 10 years as electronics became smaller and more sophisticated. They begin with number 57 Lanthanum and end with 71 Lutetium, a group of metallic chemical elements that are not rare as much as they are just difficult to mine because they occur in tiny amounts and are often stuck to each other.

Unlike metals higher up on the table such as silver and gold, there's no good agent for dissolving elements so closely linked in atomic structure without destroying the target. It makes mining for them tedious and expensive.

"The reason they haven't been explored for in the U.S. was because as long as China was prepared to export enough rare earths to fill the demand, everything was fine — like with the oil cartels. When China began to use them as a political tool, people began to see the vulnerability to the U.S. economy to having one source of rare earth elements," said Ian Ridley, director of the USGS Central Mineral and Environmental Resources Science Center in Colorado.

Two years ago, China raised prices — in the case of Neodymium, used to make Prius electric motors stronger and lighter, from $15 a kilogram in 2009 to $500 in 2011, while Dysprosium oxide used in lasers and halide lamps went from $114 a kilogram in 2010 to $2,830 in 2011. It's also about the time China cut off supplies to Japan, maker of the Prius, in a dispute over international fishing territory.

That's when the U.S. government went into emergency mode and sent geologists to hunt for new domestic sources.

"What we have is a clash of supply and demand. It's a global problem. A growing middle class around the world means more and more people want things like cellphones," said Alex King, director of the Critical Materials Institute of the Department of Energy's Ames Research Lab in Iowa. "Our job is to solve the problem any way we can."

At the University of Nevada-Reno and the Colorado School of Mines, USGS scientists used lasers to examine extensive samples of rocks and ore collected across the West during the gold rush days by geologists from Stanford University and Cal Tech.

"If we could recycle some of this waste and get something out of it that was waste years ago that isn't waste today, that certainly is a goal," said Alan Koenig, the USGS scientist in charge of the tailings project.